1. Origin of the Invention
The invention disclosed herein was made in the performance of work under a NASA contract and is subject to Public Law 96-517 (35 U.S.C. .sctn.200 et seq.). The contractor has elected to not retain title in this invention.
2. Field of the Invention
The present invention relates to a flexible ceramic thermal protection system (TPS) capable of surviving exposure to a high aeroacoustic noise level (170 decibel or greater) under fluctuating air loads, high temperature, and dynamic pressure conditions without the use or necessity of a surface coating to toughen the surface to the aeroacoustic load. The TPS is derived from an integrally woven ceramic core structure filled with a ceramic insulation possessing high temperature stability and low thermal conductivity insulation properties.
3. Description of Related Art
Conventional ceramic insulation blankets are usually assembled in a sandwich-like construction in which a layer of ceramic insulation is placed between a single-ply top or face fabric and a bottom single-ply fabric and held together with a ceramic sewing thread in a quilted stitch pattern. Sewn blankets can use other ceramic fabrics besides silica. Another blanket configuration utilizes an integrally woven single-ply core structure filled with insulation. This thermal blanket is reported in the literature as Tailorable Advanced Blanket Insulation (TABI).
Disadvantages of Prior Art--The stitched blanket (held together with a sewing thread) can fail during exposure to fluctuating pressures and high aeroacoustic loads, e.g. 170 decibels and a dynamic pressure of 510 pounds per square foot (psf). This failure occurs after exposure to a radiant heat source as low as 10 minutes (min) at 1200.degree. F. In some cases, the thread or threads start breaking within one min and can propagate into fraying or tearing the surface fabric causing rapid destruction of the surface fabric followed by removal or loss of the insulation material. This loss renders the thermal insulation blanket useless for its intended purpose.
A single ply woven TABI, which utilizes an integral weave structure woven from 1800 denier silicon carbide yarn, when filled with silica batting will quickly show fabric fraying as well as movement of the insulation in the core or cell of the TABI structure. This occurs as low as 10 min at 1440.degree. F. exposure to a radiant heat source and similar sound pressure levels and dynamic pressures as the sewn, quilted blankets.
This destructive result limits both these thermal blankets to low aeroacoustic and low temperature applications thereby minimizing the advantage of flexible ceramic blankets for applications, particularly in situations where acoustic resistance is required without resorting to or requiring a surface ceramic coating to toughen the surface fabric. These coatings can also degrade or-interact with the ceramic fabric when cured at or exposed to high temperatures. The coating also adds weight.
Some art of interest is:
S. R. Riccitiello, et al. in U.S. Pat. No. 4,713,275 disclose a rigid ceramic reusable externally applied thermal protection system.
A. R. Campman, et al. in U.S. Pat. No. 4,922,969 disclose a multilayer woven fabric having varying material composition through its thickness.
D. A. Kourtides, et al. in U.S. Pat. No. 5,038,693 disclose composite flexible multilayer insulation systems consisting of alternating layers of metal foil and ceramic scrim cloth or vacuum metallized polymeric films quilted together using a ceramic thread.
H. Goldstein et al., "Improved Thermal Protection System for the Space Shuttle Orbiter." AIAA Paper 82-0630, May 1982.
B. Trujillo, et al., "In-Flight Load Testing of Advanced Shuttle Thermal Protection Systems." AIAA Paper 83-2704, Nov. 1983.
P. M. Sawko, et al., "Effect of Processing Treatments of Strength of Silica Thread for Quilted Ceramic Insulation on Space Shuttle." SAMPE Ouarterly, Vol. 6, No. 4, July 1985, pp. 17-12.
P. M. Sawko, et al., "Performance of Uncoated AFRSI Blankets during Multiple Space Shuttle Flights." NASA Technical Memorandum 103892, April, 1992.
D. Mui, et al., "Development of a Protective Ceramic Coating for Shuttle Orbiter Advanced Flexible Reusable Surface Insulation (AFRSI)." Ceramic Eng. and Sci. Proc., Vol. 6, No. 7-8, Jul.-Aug. 1985, pp. 793-805.
P. M. Sawko, "Flexible Thermal Protection Materials." NASA CP-2315, 1983, pp. 179-183.
P. M. Sawko, "Tailored Advanced Blanket Insulation (TABI)." NASA CP-3001, 1987, pp. 135-152.
D. P. Calamito, "Tailorable Advanced Blanket Insulation Using Aluminoborosilicate and Alumina Batting," Final Report. NASA CR-177527, July 1989.
C. F. Coe, "An Assessment of Wind Tunnel Test Data on Flexible Thermal Protection Materials and Results of New Fatigue Tests of Threads," Final Report. NASA CR 177466, April 1985.
C. F. Coe, "An Investigation of the Causes of Failure of Flexible Thermal Protection Materials in an Aerodynamic Environment," Final Report, NASA CR-166624, March 1987.
H. K. Larson, et al., "Space Shuttle Orbiter Thermal Protection Material Development and Testing," Proceedings of 4th Aerospace Testing Seminar, 1978, pp. 189-193.
P. M. Sawko, et al., "Development of a Silicon Carbide Sewing Thread." SAMPE Quarterly, vol. 20, No. 4, July 1989, pp. 3-8.
P. M. Sawko, et al., "Strength and Flexibility Properties of Advanced Ceramic Fabrics." SAMPE Quarterly, Vol. 17, No. 1, Oct. 1985.
H. K. Tran, et al., "Thermal Degradation Study of Silicon Carbide Threads Developed for Advanced Thermal Protection Systems." NASA Technical Memorandum 103952, August 1992.
None of these references individually or collectively teach or suggest the present invention.
All articles, publications, books, journals, patents and patent applications and the like are incorporated by reference in their entirety.
What is needed is an integrated design and identification of materials which produce a flexible ceramic thermal protection system which has improved mechanical, thermal and sonic properties to high aeroacoustic noise (i.e. preferably about 2000.degree. F., about 2300.degree. or 2400.degree. F. for 10 min, or 2500.degree. F. for 5 min). The present invention accomplishes these objectives.